The credibility of the world's climate change authority has taken another hit, with accusations that it based a claim about disappearing forests on a report by environmental activists.

The United Nations Intergovernmental Panel on Climate Change (IPCC) cited a report by the environment group WWF to back the claim that large tracts of Amazonian forests will disappear because of diminishing rainfall.

Previously, an article in the Sunday Telegraph reported the IPCC admitted it was a mistake to claim that Himalayan glaciers will melt by the year 2035.

Now an article in London's Sunday Times carries the headline "UN climate panel shamed by bogus rainforest claim".

The article questions the IPCC's decision to cite a WWF report to support its claim that 40 per cent of Amazonian forests could disappear as a response to declining rainfall and even be replaced by tropical savannah.

WWF Australia chief executive Greg Bourne says that is not what the WWF report said and he wants to know where the IPCC conclusion came from.

"My understanding is that in the fourth session report, whilst they were looking at all the detail, they then cited one of our reports," he said.

He says the report from 2000 was misinterpreted and then quoted by the IPCC.

"But the key thing to me is that when you are compiling from thousands of pieces of information, a report as big as the fourth assessment report, they will occasionally make small mistakes," he said.

"This, I think, was a small mistake and we'll look into where the quotation came from and I am sure IPCC will as well."

Sloppy but sound?

Vocal climate change sceptic Lord Christopher Monckton, who is in Australia for a speaking tour, has questioned whether members of the panel are profiting from climate change mitigation initiatives.

"The game is up. The science is in. The truth is out. The scare is over," he said.

But an expert on the topic says the UN body's conclusion about the Amazonian forest is still sound.

Professor William Laurance from James Cook University has been studying Amazonian forests for 14 years.

He says the IPCC's conclusion has been undermined by sloppy paperwork.

"I think that the IPCC's foundations here for saying that large expanses of the Amazon are vulnerable rest on a very strong footing and, in fact, I would say the figure 40 per cent is probably conservative," he said.

He says his opinion is backed up by major scientific journals such as Nature, Science, Ecology and Biology.

"The IPCC has clearly made a mistake here. They have cited something that is not a primary reference and obviously it has weakened the IPCC's assertion," he said.

"[It] sounds like certain journalists are picking on that... and that creates, obviously, the potential for doubting the IPCC's overall conclusions."

Mr Bourne agrees that the IPCC risks damaging its own credibility.

"It is embarrassing for the IPCC, but the climate sceptics are attacking the detail because the big picture is unequivocal and they cannot attack that," he said.